Biomedical Engineering Reference
In-Depth Information
resistance of plants to various fungal pathogens. Similarly, cotton is the
most important fi bre crop, grown worldwide and it suffers severely from
the seedling diseases caused by the fungal pathogens
R. solani, Pythium
spp. and
Fusarium
spp. Cotton plants transformed with one of the 42 kDa
endochitinase genes from
T. virens
showed a high level of resistance to
infection by
R. solani
and
A. alternata
(Emani et al. 2003).
Bananas (
Musa cavendish
) are among the most important crops in
tropical and subtropical developing countries. In fact, this fruit is a staple
food for approximately 400 million people with an annual production of
more than 88 mT (Atkinson et al. 2004, Chakrabarti et al. 2003). Black leaf
streak disease (BLSD) or Sigatoka Leaf Spot disease caused by
Mycosphaerella
fi jiensis
is one of the most devastating diseases currently threatening to
destroy the banana industry worldwide. Although, the fungus induces foliar
leaf streaks, it can lead to total plant collapse under severe infection (Chillet
et al. 2009). The development of disease-resistant banana by molecular
breeding is a necessity in view of the long life cycle, triploidy and sterility
of most edible cultivars (Khanna et al. 2004). Genetic resistance to BLSD is
clearly the best long-term solution for disease control. Since the fi rst report
on banana transformation (May et al. 1995), various improvements have
been made in transformation effi ciencies of economically important genomic
groups (AAA and AAB) of cultivated banana species (Ganapathi et al.
2001, Khanna et al. 2004, Sagi 2000). The lytic peptide MSI-99 (Chakrabarti
et al. 2003) and human lysozyme (Pei et al. 2005) have been successfully
expressed in transgenic banana and the transformed plants exhibited
improved tolerance toward both
Fusarium
and
Mycosphaerella
that causes
Panama wilt and BLSD, respectively in banana. In some previous studies
it was suggested that the expression of a single antifungal gene may result
in only limited protection that can be easily overcome by natural selection
and adaptation of the pathogen, while combinations of several antifungal
genes may result in enhanced protection which is more diffi cult to overcome
(Jach et al. 1995). Keeping it in view Vishnevetsky et al. (2011) developed
a transformation system for banana and expressed the endochitinase gene
ThEn-42 from
T. harzianum
together with the grape stilbene synthase (StSy)
gene in transgenic banana plants under the control of the 35S promoter and
the inducible PR-10 promoter, respectively. The superoxide dismutase gene
Cu, Zn-SOD from tomato, under control of the ubiquitin promoter, was
then added to this cassette to improve scavenging of free radicals generated
during fungal attack. A 4-year fi eld trial demonstrated several transgenic
banana lines with improved tolerance to Sigatoka. Further to test whether
the genes conferring Sigatoka tolerance will have a wide range of anti-
fungal activities they also inoculated the regenerated banana plants with
B.
cinerea
and it was observed that the best transgenic lines exhibiting Sigatoka
tolerance were also found to have tolerance to
B. cinerea
(Vishnevetsky et al.
